Methods and apparatus for user equipment to differentiate human grip from protective covers

ABSTRACT

Methods and apparatus for distinguishing between an antenna of a user equipment (UE) being blocked by a cover (e.g., a protective rubber or plastic case) or by human tissue (e.g., a finger or palm). The transmission power of uplink (UL) signals may be adjusted accordingly, with relatively higher transmission power for open space or a cover and relatively lower transmission power for human tissue. One example method for wireless communications by a UE generally includes transmitting a first signal from the UE, receiving a plurality of signals at the UE based on the transmitted first signal, determining values for at least two different types of parameters based on the received plurality of signals, determining an environmental scenario for the UE based on the values for the at least two different types of parameters, and transmitting a second signal using a transmission power based on the determined environmental scenario.

CLAIM OF PRIORITY UNDER 35 U.S.C. §§ 119 AND 120

This application is a continuation application of U.S. application Ser.No. 16/898,746, entitled “Methods and Apparatus for User Equipment toDifferentiate Human Grip from Protective Covers” filed Jun. 11, 2020,which claims benefit of and priority to U.S. Provisional PatentApplication No. 62/860,608, entitled “Methods and Apparatus for UserEquipment to Differentiate Human Grip from Protective Covers” and filedJun. 12, 2019, each of which is expressly incorporated herein in itsentirety.

TECHNICAL FIELD

Certain aspects of the present disclosure generally relate to wirelessdevices and, more particularly, to differentiating between human gripand a protective cover on a wireless device.

BACKGROUND

Modern wireless devices (such as cellular phones) are generally requiredto meet radio frequency (RF) exposure limits set by domestic andinternational standards and regulations. To ensure compliance with thestandards, such devices must currently undergo an extensivecertification process prior to being shipped to market. To ensure that awireless device complies with an RF exposure limit, techniques have beendeveloped to enable the wireless device to assess RF exposure from thewireless device in real time and adjust the transmission power of thewireless device accordingly to comply with the RF exposure limit.

SUMMARY

The systems, methods, and devices of the disclosure each have severalaspects, no single one of which is solely responsible for its desirableattributes. Without limiting the scope of this disclosure as expressedby the claims which follow, some features will now be discussed briefly.After considering this discussion, and particularly after reading thesection entitled “Detailed Description,” one will understand how thefeatures of this disclosure provide advantages that include improvedsystems and methods for assessing RF exposure from a wireless device.

Certain aspects of the present disclosure provide a method for wirelesscommunications by a user equipment (UE). The method generally includestransmitting a first signal from the UE, receiving a plurality ofsignals at the UE based on the transmitted first signal, determiningvalues for at least two different types of parameters based on thereceived plurality of signals, determining an environmental scenario forthe UE based on the values for the at least two different types ofparameters, and transmitting a second signal using a transmission powerbased on the determined environmental scenario.

Certain aspects of the present disclosure are directed to an apparatusfor wireless communications. The apparatus includes a transmitter, areceiver, and a processing system. The transmitter is configured totransmit a first signal from the apparatus, and the receiver isconfigured to receive a plurality of signals based on the transmittedfirst signal. The processing system is configured to determine valuesfor at least two different types of parameters based on the receivedplurality of signals and to determine an environmental scenario for theapparatus based on the values for the at least two different types ofparameters. The transmitter is further configured to transmit a secondsignal using a transmission power based on the determined environmentalscenario.

Certain aspects of the present disclosure are directed to an apparatusfor wireless communications. The apparatus generally includes means fortransmitting a first signal, means for receiving a plurality of signalsbased on the transmitted first signal, means for determining values forat least two different types of parameters based on the receivedplurality of signals, means for determining an environmental scenariofor the apparatus based on the values for the at least two differenttypes of parameters, and means for transmitting a second signal using atransmission power based on the determined environmental scenario.

Certain aspects of the present disclosure are directed to anon-transitory computer-readable medium having instructions, which whenexecuted by a processing system, cause the processing system to performoperations for wireless communications by a UE. The operations generallyinclude controlling transmission of a first signal from the UE,controlling reception of a plurality of signals based on the transmittedfirst signal, determining values for at least two different types ofparameters based on the received plurality of signals, determining anenvironmental scenario for the UE based on the values for the at leasttwo different types of parameters, and controlling transmission of asecond signal using a transmission power based on the determinedenvironmental scenario.

Certain aspects of the present disclosure provide a method for wirelesscommunications by a UE. The method generally includes transmitting afirst signal from the UE; receiving a plurality of signals at the UEbased on the transmitted first signal; determining a value for each ofone or more parameters based on the received plurality of signals;determining a type of a cover adjacent to an antenna array of the UEbased on the value for each of the one or more parameters; selecting anantenna array codebook based on the determined type of the cover; andtransmitting a second signal according to the selected antenna arraycodebook.

Certain aspects of the present disclosure are directed to an apparatusfor wireless communications. The apparatus includes an antenna array, atransmitter, a receiver, and a processing system. The transmitter iscoupled to the antenna array and configured to transmit a first signalvia the antenna array. The receiver is coupled to the antenna array andconfigured to receive, via the antenna array, a plurality of signalsbased on the transmitted first signal. The processing system is coupledto the receiver and configured to determine a value for each of one ormore parameters based on the received plurality of signals, to determinea type of a cover adjacent to the antenna array of the apparatus basedon the value for each of the one or more parameters, and to select anantenna array codebook based on the determined type of the cover. Thetransmitter is further configured to transmit, via the antenna array, asecond signal according to the selected antenna array codebook.

Certain aspects of the present disclosure are directed to an apparatusfor wireless communications. The apparatus generally includes means fortransmitting a first signal from the apparatus; means for receiving aplurality of signals based on the transmitted first signal; means fordetermining a value for each of one or more parameters based on thereceived plurality of signals; means for determining a type of a coveradjacent to an antenna array of the apparatus based on the value foreach of the one or more parameters; means for selecting an antenna arraycodebook based on the determined type of the cover; and means fortransmitting a second signal according to the selected antenna arraycodebook.

Certain aspects of the present disclosure are directed to anon-transitory computer-readable medium having instructions, which whenexecuted by a processing system, cause the processing system to performoperations for wireless communications by a UE. The operations generallyinclude controlling transmission of a first signal from the UE;controlling reception of a plurality of signals based on the transmittedfirst signal; determining a value for each of one or more parametersbased on the received plurality of signals; determining a type of acover adjacent to an antenna array of the UE based on the value for eachof the one or more parameters; selecting an antenna array codebook basedon the determined type of the cover; and controlling transmission of asecond signal according to the selected antenna array codebook.

To the accomplishment of the foregoing and related ends, the one or moreaspects comprise the features hereinafter fully described andparticularly pointed out in the claims. The following description andthe annexed drawings set forth in detail certain illustrative featuresof the one or more aspects. These features are indicative, however, ofbut a few of the various ways in which the principles of various aspectsmay be employed, and this description is intended to include all suchaspects and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the presentdisclosure can be understood in detail, a more particular description,briefly summarized above, may be had by reference to aspects, some ofwhich are illustrated in the appended drawings. It is to be noted,however, that the appended drawings illustrate only certain typicalaspects of this disclosure and are therefore not to be consideredlimiting of its scope, for the description may admit to other equallyeffective aspects.

FIG. 1 is a block diagram conceptually illustrating an exampletelecommunications system, in accordance with certain aspects of thepresent disclosure.

FIG. 2 is a block diagram conceptually illustrating a design of anexample base station (BS) and an example user equipment (UE), inaccordance with certain aspects of the present disclosure.

FIG. 3 is a block diagram showing an example transceiver front-end, inaccordance with certain aspects of the present disclosure.

FIG. 4A illustrates millimeter wave (mmW) sensing by a UE, in accordancewith certain aspects of the present disclosure.

FIG. 4B illustrates mmW sensing using cross-polarization (Xpol), inaccordance with certain aspects of the present disclosure.

FIG. 4C illustrates mmW sensing using frequency-modulatedcontinuous-wave (FMCW) radar, in accordance with certain aspects of thepresent disclosure.

FIG. 5 illustrates example fast Fourier transform (FFT) symbol valuesfrom Xpol detection, in accordance with certain aspects of the presentdisclosure.

FIG. 6 is an example plot of cross-polarization ratios (K) in thein-phase/quadrature (IQ) plane for detection of an object in front of anantenna, in accordance with certain aspects of the present disclosure.

FIG. 7 is a flow diagram of example operations for wirelesscommunications, in accordance with certain aspects of the presentdisclosure.

FIG. 8 is an example plot of signal-to-noise ratio (SNR) in decibels(dB) of vertical and horizontal polarization components for differentscenarios, in accordance with certain aspects of the present disclosure.

FIG. 9 illustrates an example correlation between standard deviation ofK values (GK) and the mean signal-to-noise ratio (SNR_(m)) of thevertical and horizontal polarization components for different scenarios,in accordance with certain aspects of the present disclosure.

FIG. 10 illustrates an example linear relationship between σ_(K) andSNR_(m) for different scenarios, where the line represents a boundarybetween open space (OS) versus detection boundary, in accordance withcertain aspects of the present disclosure.

FIG. 11 is a flow chart for determining parameters for OS based on σ_(K)and SNR_(m), in accordance with certain aspects of the presentdisclosure.

FIG. 12 is a flow diagram of example operations for wirelesscommunications based on antenna array codebook selection, in accordancewith certain aspects of the present disclosure.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

Certain aspects of the present disclosure provide techniques andapparatus for distinguishing between an antenna of a user equipment (UE)being blocked by a cover (e.g., a protective rubber or plastic cover) orby human tissue (e.g., a finger or palm). The transmission power ofuplink (UL) signals may be adjusted accordingly, with relatively highertransmission power for open space or a cover and relatively lowertransmission power for human tissue.

The following description provides examples, and is not limiting of thescope, applicability, or examples set forth in the claims. Changes maybe made in the function and arrangement of elements discussed withoutdeparting from the scope of the disclosure. Various examples may omit,substitute, or add various procedures or components as appropriate. Forinstance, the methods described may be performed in an order differentfrom that described, and various steps may be added, omitted, orcombined. Also, features described with respect to some examples may becombined in some other examples. For example, an apparatus may beimplemented or a method may be practiced using any number of the aspectsset forth herein. In addition, the scope of the disclosure is intendedto cover such an apparatus or method which is practiced using otherstructure, functionality, or structure and functionality in addition to,or other than, the various aspects of the disclosure set forth herein.It should be understood that any aspect of the disclosure disclosedherein may be embodied by one or more elements of a claim. The word“exemplary” is used herein to mean “serving as an example, instance, orillustration.” Any aspect described herein as “exemplary” is notnecessarily to be construed as preferred or advantageous over otheraspects.

The techniques described herein may be used for various wirelesscommunication technologies, such as LTE, CDMA, TDMA, FDMA, OFDMA,SC-FDMA and other networks. The terms “network” and “system” are oftenused interchangeably. A CDMA network may implement a radio technologysuch as Universal Terrestrial Radio Access (UTRA), cdma2000, etc. UTRAincludes Wideband CDMA (WCDMA) and other variants of CDMA. cdma2000covers IS-2000, IS-95 and IS-856 standards. A TDMA network may implementa radio technology such as Global System for Mobile Communications(GSM). An OFDMA network may implement a radio technology such as NR(e.g. 5G RA), Evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDMA, etc. UTRAand E-UTRA are part of Universal Mobile Telecommunication System (UMTS).

New Radio (NR) is an emerging wireless communications technology underdevelopment in conjunction with the 5G Technology Forum (5GTF). 3GPPLong Term Evolution (LTE) and LTE-Advanced (LTE-A) are releases of UMTSthat use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A and GSM are described indocuments from an organization named “3rd Generation PartnershipProject” (3GPP). cdma2000 and UMB are described in documents from anorganization named “3rd Generation Partnership Project 2” (3GPP2). Thetechniques described herein may be used for the wireless networks andradio technologies mentioned above as well as other wireless networksand radio technologies. For clarity, while aspects may be describedherein using terminology commonly associated with 3G and/or 4G wirelesstechnologies, aspects of the present disclosure can be applied in othergeneration-based communication systems, such as 5G and later, includingNR technologies.

NR access (e.g., 5G technology) may support various wirelesscommunication services, such as enhanced mobile broadband (eMBB)targeting wide bandwidth (e.g., 80 MHz or beyond), millimeter wave (mmW)targeting high carrier frequency (e.g., 25 GHz or beyond), massivemachine type communications MTC (mMTC) targeting non-backward compatibleMTC techniques, and/or mission critical targeting ultra-reliablelow-latency communications (URLLC). These services may include latencyand reliability requirements. These services may also have differenttransmission time intervals (TTI) to meet respective quality of service(QoS) requirements. In addition, these services may co-exist in the samesubframe.

Example Wireless Communications System

FIG. 1 illustrates an example wireless communications network 100 inwhich aspects of the present disclosure may be performed. Wirelessdevices in the wireless network 100 may perform the methods fordetermining an environmental scenario for an antenna (or antenna array)of the wireless device as further described herein. As used herein, an“environmental scenario” generally refers to the antenna (or antennaarray) of the wireless device being blocked by an object (such as aprotective cover or human grip) or not being blocked by an object (acondition referred to as “open space”).

As illustrated in FIG. 1, the wireless network 100 may include a numberof base stations (BSs) 110 and other network entities. A BS may be astation that communicates with user equipments (UEs). Each BS 110 mayprovide communication coverage for a particular geographic area. In3GPP, the term “cell” can refer to a coverage area of a Node B (NB)and/or a Node B subsystem serving this coverage area, depending on thecontext in which the term is used. In NR systems, the term “cell” andnext generation Node B (gNB), new radio base station (NR BS), 5G NB,access point (AP), or transmission reception point (TRP) may beinterchangeable. In some examples, a cell may not necessarily bestationary, and the geographic area of the cell may move according tothe location of a mobile BS. In some examples, the base stations may beinterconnected to one another and/or to one or more other base stationsor network nodes (not shown) in wireless communication network 100through various types of backhaul interfaces, such as a direct physicalconnection, a wireless connection, a virtual network, or the like usingany suitable transport network.

In general, any number of wireless networks may be deployed in a givengeographic area. Each wireless network may support a particular radioaccess technology (RAT) and may operate on one or more frequencies. ARAT may also be referred to as a radio technology, an air interface,etc. A frequency may also be referred to as a carrier, a subcarrier, afrequency channel, a tone, a subband, etc. Each frequency may support asingle RAT in a given geographic area in order to avoid interferencebetween wireless networks of different RATs. In some cases, NR or 5G RATnetworks may be deployed.

A base station (BS) may provide communication coverage for a macro cell,a pico cell, a femto cell, and/or other types of cells. A macro cell maycover a relatively large geographic area (e.g., several kilometers inradius) and may allow unrestricted access by UEs with servicesubscription. A pico cell may cover a relatively small geographic areaand may allow unrestricted access by UEs with service subscription. Afemto cell may cover a relatively small geographic area (e.g., a home)and may allow restricted access by UEs having an association with thefemto cell (e.g., UEs in a Closed Subscriber Group (CSG), UEs for usersin the home, etc.). A BS for a macro cell may be referred to as a macroBS. A BS for a pico cell may be referred to as a pico BS. A BS for afemto cell may be referred to as a femto BS or a home BS. In the exampleshown in FIG. 1, the BSs 110 a, 110 b, and 110 c may be macro BSs forthe macro cells 102 a, 102 b, and 102 c, respectively. The BS 110 x maybe a pico BS for a pico cell 102 x. The BSs 110 y and 110 z may be femtoBSs for the femto cells 102 y and 102 z, respectively. A BS may supportone or multiple (e.g., three) cells.

Wireless communication network 100 may also include relay stations. Arelay station is a station that receives a transmission of data and/orother information from an upstream station (e.g., a BS or a UE) andsends a transmission of the data and/or other information to adownstream station (e.g., a UE or a BS). A relay station may also be aUE that relays transmissions for other UEs. In the example shown in FIG.1, a relay station 110 r may communicate with the BS 110 a and a UE 120r in order to facilitate communication between the BS 110 a and the UE120 r. A relay station may also be referred to as a relay BS, a relay,etc.

Wireless network 100 may be a heterogeneous network that includes BSs ofdifferent types, e.g., macro BS, pico BS, femto BS, relays, etc. Thesedifferent types of BSs may have different transmit power levels,different coverage areas, and different impact on interference in thewireless network 100. For example, a macro BS may have a high transmitpower level (e.g., 20 watts (W)) whereas a pico BS, a femto BS, andrelays may have a lower transmit power level (e.g., 1 W).

Wireless communication network 100 may support synchronous orasynchronous operation. For synchronous operation, the BSs may havesimilar frame timing, and transmissions from different BSs may beapproximately aligned in time. For asynchronous operation, the BSs mayhave different frame timing, and transmissions from different BSs maynot be aligned in time. The techniques described herein may be used forboth synchronous and asynchronous operation.

A network controller 130 may couple to a set of BSs and providecoordination and control for these BSs. The network controller 130 maycommunicate with the BSs 110 via a backhaul. The BSs 110 may alsocommunicate with one another (e.g., directly or indirectly) via wirelessor wireline backhaul.

The UEs 120 (e.g., 120 x, 120 y, etc.) may be dispersed throughout thewireless network 100, and each UE may be stationary or mobile. A UE mayalso be referred to as a mobile station (MS), a terminal, an accessterminal, a subscriber unit, a station, a Customer Premises Equipment(CPE), a cellular phone, a smart phone, a personal digital assistant(PDA), a wireless modem, a wireless communication device, a handhelddevice, a laptop computer, a cordless phone, a wireless local loop (WLL)station, a tablet computer, a camera, a gaming device, a netbook, asmartbook, an ultrabook, an appliance, a medical device or medicalequipment, a biometric sensor/device, a wearable device such as a smartwatch, smart clothing, smart glasses, a smart wrist band, smart jewelry(e.g., a smart ring, a smart bracelet, etc.), an entertainment device(e.g., a music device, a video device, a satellite radio, etc.), avehicular component or sensor, a smart meter/sensor, industrialmanufacturing equipment, a Global Positioning System (GPS) device, orany other suitable device that is configured to communicate via awireless or wired medium. Some UEs may be considered machine-typecommunication (MTC) devices or evolved MTC (eMTC) devices. MTC and eMTCUEs include, for example, robots, drones, remote devices, sensors,meters, monitors, location tags, etc., that may communicate with a BS,another device (e.g., remote device), or some other entity. A wirelessnode may provide, for example, connectivity for or to a network (e.g., awide area network such as Internet or a cellular network) via a wired orwireless communication link. Some UEs may be consideredInternet-of-Things (IoT) devices, which may be narrowband IoT (NB-IoT)devices.

Certain wireless networks (e.g., LTE) utilize orthogonal frequencydivision multiplexing (OFDM) on the downlink and single-carrierfrequency division multiplexing (SC-FDM) on the uplink. OFDM and SC-FDMpartition the system bandwidth into multiple (K) orthogonal subcarriers,which are also commonly referred to as tones, bins, etc. Each subcarriermay be modulated with data. In general, modulation symbols are sent inthe frequency domain with OFDM and in the time domain with SC-FDM. Thespacing between adjacent subcarriers may be fixed, and the total numberof subcarriers (K) may be dependent on the system bandwidth. Forexample, the spacing of the subcarriers may be 15 kHz, and the minimumresource allocation (called a “resource block” (RB)) may be 12subcarriers (or 180 kHz). Consequently, the nominal fast Fouriertransform (FFT) size may be equal to 128, 256, 512, 1024, or 2048 for asystem bandwidth of 1.25, 2.5, 5, 10, or 20 megahertz (MHz),respectively. The system bandwidth may also be partitioned intosubbands. For example, a subband may cover 1.08 MHz (i.e., 6 resourceblocks), and there may be 1, 2, 4, 8, or 16 subbands for a systembandwidth of 1.25, 2.5, 5, 10, or 20 MHz, respectively.

While aspects of the examples described herein may be associated withLTE technologies, aspects of the present disclosure may be applicablewith other wireless communications systems, such as NR. NR may utilizeOFDM with a cyclic prefix (CP) on the uplink and downlink and includesupport for half-duplex operation using time-division duplexing (TDD).Beamforming may be supported, and beam direction may be dynamicallyconfigured. Multiple-input, multiple-output (MIMO) transmissions withprecoding may also be supported. MIMO configurations in the downlink(DL) may support up to 8 transmit antennas with multi-layer DLtransmissions up to 8 streams and up to 2 streams per UE. Aggregation ofmultiple cells may be supported with up to 8 serving cells.

In some examples, access to the air interface may be scheduled, whereina scheduling entity (e.g., a base station) allocates resources forcommunication among some or all devices and equipment within its servicearea or cell. The scheduling entity may be responsible for scheduling,assigning, reconfiguring, and releasing resources for one or moresubordinate entities. That is, for scheduled communication, subordinateentities utilize resources allocated by the scheduling entity. Basestations are not the only entities that may function as a schedulingentity. In some examples, a UE may function as a scheduling entity andmay schedule resources for one or more subordinate entities (e.g., oneor more other UEs), and the other UEs may utilize the resourcesscheduled by the UE for wireless communication. In some examples, a UEmay function as a scheduling entity in a peer-to-peer (P2P) network,and/or in a mesh network. In a mesh network example, UEs may communicatedirectly with one another in addition to communicating with a schedulingentity.

In FIG. 1, a solid line with double arrows indicates desiredtransmissions between a UE and a serving BS, which is a BS designated toserve the UE on the downlink and/or uplink. A dashed line with doublearrows indicates interfering transmissions between a UE and a BS.

FIG. 2 illustrates example components of BS 110 and UE 120 (as depictedin FIG. 1), which may be used to implement aspects of the presentdisclosure. For example, antennas 252, transceiver (TX/RX) front-endcircuits 254, processors 258, 264, and/or controller/processor 280 ofthe UE 120 may be used to perform the various techniques and methodsdescribed herein (e.g., operations 700 of FIG. 7 or operations 1200 ofFIG. 12).

At the BS 110, a transmit processor 220 may receive data from a datasource 212 and control information from a controller/processor 240. Thecontrol information may be for the physical broadcast channel (PBCH),physical control format indicator channel (PCFICH), physical hybrid ARQindicator channel (PHICH), physical downlink control channel (PDCCH),group common PDCCH (GC PDCCH), etc. The data may be for the physicaldownlink shared channel (PDSCH), etc. The processor 220 may process(e.g., encode and symbol map) the data and control information to obtaindata symbols and control symbols, respectively. The processor 220 mayalso generate reference symbols, e.g., for the primary synchronizationsignal (PSS), secondary synchronization signal (SSS), and cell-specificreference signal (CRS). A transmit (TX) multiple-input multiple-output(MIMO) processor 230 may perform spatial processing (e.g., precoding) onthe data symbols, the control symbols, and/or the reference symbols, ifapplicable, and may provide output symbol streams to the transmit (TX)front-end circuits 232 a through 232 t. Each TX front-end circuit 232may process a respective output symbol stream (e.g., for OFDM, etc.) toobtain an output sample stream. Each TX front-end circuit 232 mayfurther process (e.g., convert to analog, amplify, filter, andupconvert) the output sample stream to obtain a downlink signal.Downlink signals from TX front-end circuits 232 a through 232 t may betransmitted via the antennas 234 a through 234 t, respectively.

At the UE 120, the antennas 252 a through 252 r may receive the downlinksignals from the BS 110 and may provide received signals to the receive(RX) front-end circuits 254 a through 254 r, respectively. Each RXfront-end circuit 254 may condition (e.g., filter, amplify, downconvert,and digitize) a respective received signal to obtain input samples. EachRX front-end circuit 254 may further process the input samples (e.g.,for OFDM, etc.) to obtain received symbols. A MIMO detector 256 mayobtain received symbols from all the RX front-end circuits 254 a through254 r, perform MIMO detection on the received symbols if applicable, andprovide detected symbols. A receive processor 258 may process (e.g.,demodulate, deinterleave, and decode) the detected symbols, providedecoded data for the UE 120 to a data sink 260, and provide decodedcontrol information to a controller/processor 280. Memory 282 may storedata and program codes for the UE 120 and may interface with thecontroller/processor 280.

On the uplink, at UE 120, a transmit processor 264 may receive andprocess data (e.g., for the physical uplink shared channel (PUSCH)) froma data source 262 and control information (e.g., for the physical uplinkcontrol channel (PUCCH) from the controller/processor 280. The transmitprocessor 264 may also generate reference symbols for a reference signal(e.g., for the sounding reference signal (SRS)). The symbols from thetransmit processor 264 may be precoded by a TX MIMO processor 266 ifapplicable, further processed by the RX front-end circuits 254 a through254 r (e.g., for SC-FDM, etc.), and transmitted to the BS 110. At the BS110, the uplink signals from the UE 120 may be received by the antennas234, processed by the TX front-end circuits 232, detected by a MIMOdetector 236 if applicable, and further processed by a receive processor238 to obtain decoded data and control information sent by the UE 120.The receive processor 238 may provide the decoded data to a data sink239 and the decoded control information to the controller/processor 240.Memory 242 may store data and program codes for the BS 110 and mayinterface with the controller/processor 240.

The controllers/processors 240 and 280 may direct the operation at theBS 110 and the UE 120, respectively. The processor 240 and/or otherprocessors and modules at the BS 110 may perform or direct the executionof processes for the techniques described herein. The memories 242 and282 may store data and program codes for BS 110 and UE 120,respectively. A scheduler 244 may schedule UEs for data transmission onthe downlink and/or uplink.

FIG. 3 is a block diagram of an example transceiver front-end 300, suchas TX/RX front-end circuits 232, 254 in FIG. 2, in accordance withcertain aspects of the present disclosure. The transceiver front-end 300includes at least one transmit (TX) path 302 (also known as a “transmitchain”) for transmitting signals via one or more antennas and at leastone receive (RX) path 304 (also known as a “receive chain”) forreceiving signals via the antennas. When the TX path 302 and the RX path304 share an antenna 303, the paths may be connected with the antennavia an RF interface 306, which may include any of various suitable RFdevices, such as a duplexer, a switch, a diplexer, and the like.

Receiving in-phase (I) or quadrature (Q) baseband analog signals from adigital-to-analog converter (DAC) 308, the TX path 302 may include abaseband filter (BBF) 310, a mixer 312, a driver amplifier (DA) 314, anda power amplifier (PA) 316. The BBF 310, the mixer 312, and the DA 314may be included in a radio frequency integrated circuit (RFIC), whilethe PA 316 may be included in the RFIC or external to the RFIC. The BBF310 filters the baseband signals received from the DAC 308, and themixer 312 mixes the filtered baseband signals with a transmit localoscillator (LO) signal to convert the baseband signal of interest to adifferent frequency (e.g., upconvert from baseband to RF). Thisfrequency conversion process produces the sum and difference frequenciesbetween the LO frequency and the frequencies of the baseband signal ofinterest. The sum and difference frequencies are referred to as the beatfrequencies. The beat frequencies are typically in the RF range, suchthat the signals output by the mixer 312 are typically RF signals, whichmay be amplified by the DA 314 and/or by the PA 316 before transmissionby the antenna 303.

The RX path 304 may include a low noise amplifier (LNA) 322, a mixer324, and a baseband filter (BBF) 326. The LNA 322, the mixer 324, andthe BBF 326 may be included in a radio frequency integrated circuit(RFIC), which may or may not be the same RFIC that includes the TX pathcomponents. RF signals received via the antenna 303 may be amplified bythe LNA 322, and the mixer 324 mixes the amplified RF signals with areceive local oscillator (LO) signal to convert the RF signal ofinterest to a different baseband frequency (i.e., downconvert). Thebaseband signals output by the mixer 324 may be filtered by the BBF 326before being converted by an analog-to-digital converter (ADC) 328 todigital I or Q signals for digital signal processing.

While it is desirable for the output of an LO to remain stable infrequency, tuning to different frequencies may indicate using avariable-frequency oscillator, which can involve compromises betweenstability and tunability. Contemporary systems may employ frequencysynthesizers with a voltage-controlled oscillator (VCO) to generate astable, tunable LO with a particular tuning range. Thus, the transmit LOmay be produced by a TX frequency synthesizer 318, which may be bufferedor amplified by amplifier 320 before being mixed with the basebandsignals in the mixer 312. Similarly, the receive LO may be produced byan RX frequency synthesizer 330, which may be buffered or amplified byamplifier 332 before being mixed with the RF signals in the mixer 324.

Example RF Exposure Assessment

RF exposure may be expressed in terms of a specific absorption rate(SAR), which measures energy absorption by human tissue per unit massand may have units of watts per kilogram (W/kg). Alternatively, RFexposure may be expressed in terms of power density (PD), which measuresenergy absorption per unit area and may have units of mW/cm^(2.)

SAR may be used to assess RF exposure for transmission frequencies lessthan 6 GHz, which cover wireless communication technologies such as 3G(e.g., CDMA), 4G (e.g., LTE), 5G (e.g., NR in 6 GHz bands), IEEE 802.11ac, etc. PD may be used to assess RF exposure for transmissionfrequencies higher than 10 GHz, which cover wireless communicationtechnologies such as IEEE 802.11ad, 802.11ay, 5G, etc. Thus, differentmetrics may be used to assess RF exposure for different wirelesscommunication technologies.

A wireless device (e.g., UE 120) may simultaneously transmit signalsusing multiple wireless communication technologies. For example, thewireless device may simultaneously transmit signals using a firstwireless communication technology operating at or below 6 GHz (e.g., 3G,4G, 5G, etc.) and a second wireless communication technology operatingabove 6 GHz (e.g., 5G in 24 to 60 GHz bands, IEEE 802.11ad or 802.11ay).In certain aspects, the wireless device may simultaneously transmitsignals using the first wireless communication technology (e.g., 3G, 4G,5G in 6 GHz bands, IEEE 802.11ac, etc.) in which RF exposure is measuredin terms of SAR, and the second wireless communication technology (e.g.,5G in 24 to 60 GHz bands, IEEE 802.11ad, 802.11ay, etc.) in which RFexposure is measured in terms of PD.

To assess RF exposure from transmissions using the first technology(e.g., 3G, 4G, 5G in 6 GHz bands, IEEE 802.11ac, etc.), the wirelessdevice may include multiple SAR distributions for the first technologystored in memory (e.g., memory 282 of FIG. 2 or memory 336 of FIG. 3).Each of the SAR distributions may correspond to a respective one ofmultiple transmit scenarios supported by the wireless device for thefirst technology. The transmit scenarios may correspond to variouscombinations of antennas (e.g., antennas 252 a through 252 r of FIG. 2or antenna 303 of FIG. 3), frequency bands, channels, and/or bodypositions, as discussed further below.

The SAR distribution (also referred to as a “SAR map”) for each transmitscenario may be generated based on measurements (e.g., E-fieldmeasurements) performed in a test laboratory using a model of a humanbody. After the SAR distributions are generated, the SAR distributionsmay be stored in the memory to enable a processor (e.g., processor 266of FIG. 2) to assess RF exposure in real time. Each SAR distributionincludes a set of SAR values, where each SAR value may correspond to adifferent location (e.g., on the model of the human body). Each SARvalue may comprise a SAR value averaged over a mass of 1 g or 10 g atthe respective location.

The SAR values in each SAR distribution correspond to a particulartransmission power level (e.g., the transmission power level at whichthe SAR values were measured in the test laboratory). Since SAR scaleswith transmission power level, the processor may scale a SARdistribution for any transmission power level by multiplying each SARvalue in the SAR distribution by the following transmission powerscaler:

$\begin{matrix}\frac{Tx_{c}}{Tx_{SAR}} & (1)\end{matrix}$

where Tx_(c) is a current transmission power level for the respectivetransmit scenario, and Tx_(SAR) is the transmission power levelcorresponding to the SAR values in the stored SAR distribution (e.g.,the transmission power level at which the SAR values were measured inthe test laboratory).

As discussed above, the wireless device may support multiple transmitscenarios for the first technology. In certain aspects, the transmitscenarios may be specified by a set of parameters. The set of parametersmay include one or more of the following: (a) an antenna parameterindicating one or more antennas used for transmission (i.e., activeantennas), (b) a frequency band parameter indicating one or morefrequency bands used for transmission (i.e., active frequency bands),(c) a channel parameter indicating one or more channels used fortransmission (i.e., active channels), (d) a body position parameterindicating the location of the wireless device relative to the user'sbody location (head, trunk, away from the body, etc.), and/or (e) otherparameters. In cases where the wireless device supports a large numberof transmit scenarios, it may be very time-consuming and expensive toperform measurements for each transmit scenario in a test setting (e.g.,test laboratory). To reduce test time, measurements may be performed fora subset of the transmit scenarios to generate SAR distributions for thesubset of transmit scenarios. In this example, the SAR distribution foreach of the remaining transmit scenarios may be generated by combiningtwo or more of the SAR distributions for the subset of transmitscenarios, as discussed further below.

For example, SAR measurements may be performed for each one of theantennas to generate a SAR distribution for each one of the antennas. Inthis example, a SAR distribution for a transmit scenario in which two ormore of the antennas are active may be generated by combining the SARdistributions for the two or more active antennas.

In another example, SAR measurements may be performed for each one ofmultiple frequency bands to generate a SAR distribution for each one ofthe multiple frequency bands. In this example, a SAR distribution for atransmit scenario in which two or more frequency bands are active may begenerated by combining the SAR distributions for the two or more activefrequency bands.

In certain aspects, a SAR distribution may be normalized with respect toa SAR limit by dividing each SAR value in the SAR distribution by theSAR limit. In this case, a normalized SAR value exceeds the SAR limitwhen the normalized SAR value is greater than one, and is below the SARlimit when the normalized SAR value is less than one. In these aspects,each of the SAR distributions stored in the memory may be normalizedwith respect to a SAR limit.

In certain aspects, the normalized SAR distribution for a transmitscenario may be generated by combining two or more normalized SARdistributions. For example, a normalized SAR distribution for a transmitscenario in which two or more antennas are active may be generated bycombining the normalized SAR distributions for the two or more activeantennas. For the case in which different transmission power levels areused for the active antennas, the normalized SAR distribution for eachactive antenna may be scaled by the respective transmission power levelbefore combining the normalized SAR distributions for the activeantennas. The normalized SAR distribution for simultaneous transmissionfrom multiple active antennas may be given by the following:

$\begin{matrix}{{SAR_{{norm\_ combine}d}} = {\sum\limits_{i = 1}^{K}{\frac{Tx_{i}}{Tx_{SARi}} \cdot \frac{SAR_{i}}{SAR_{\lim}}}}} & (2)\end{matrix}$

where SAR_(lim) is a SAR limit, SAR_(norm_combined) is the combinednormalized SAR distribution for simultaneous transmission from theactive antennas, i is an index for the active antennas, SAR_(i) is theSAR distribution for the i^(th) active antenna, Tx_(i) is thetransmission power level for the i^(th) active antenna, Tx_(SARi) is thetransmission power level for the SAR distribution for the i^(th) activeantenna, and K is the number of the active antennas.

Equation (2) may be rewritten as follows:

$\begin{matrix}{{SAR_{norm\_ combined}} = {\sum\limits_{i = 1}^{K}{{\frac{Tx_{i}}{Tx_{SARi}} \cdot {SA}}R_{{norm}\_ i}}}} & \left( {3a} \right)\end{matrix}$

where SAR_(norm_i) is the normalized SAR distribution for the i^(th)active antenna. In the case of simultaneous transmissions using multipleactive antennas at the same transmitting frequency (e.g., multiple inmultiple out (MIMO)), the combined normalized SAR distribution isobtained by summing the square root of the individual normalized SARdistributions and computing the square of the sum, as given by thefollowing:

$\begin{matrix}{{SAR_{{norm\_ combined}{\_ MIMO}}} = {\left\lbrack {\sum\limits_{i = 1}^{K}\sqrt{{\frac{Tx_{i}}{Tx_{SARi}} \cdot {SA}}R_{norm\_ i}}} \right\rbrack^{2}.}} & \left( {3b} \right)\end{matrix}$

In another example, normalized SAR distributions for different frequencybands may be stored in the memory. In this example, a normalized SARdistribution for a transmit scenario in which two or more frequencybands are active may be generated by combining the normalized SARdistributions for the two or more active frequency bands. For the casewhere the transmission power levels are different for the activefrequency bands, the normalized SAR distribution for each of the activefrequency bands may be scaled by the respective transmission power levelbefore combining the normalized SAR distributions for the activefrequency bands. In this example, the combined SAR distribution may alsobe computed using Equation (3a) in which i is an index for the activefrequency bands, SAR_(norm_i) is the normalized SAR distribution for thei^(th) active frequency band, Tx_(i) is the transmission power level forthe i^(th) active frequency band, and Tx_(SARi) is the transmissionpower level for the normalized SAR distribution for the i^(th) activefrequency band.

To assess RF exposure from transmissions using the second technology(e.g., 5G in 24 to 60 GHz bands, IEEE 802.11ad, 802.11ay, etc.), thewireless device may include multiple PD distributions for the secondtechnology stored in the memory (e.g., memory 282 of FIG. 2 or memory336 of FIG. 3). Each of the PD distributions may correspond to arespective one of multiple transmit scenarios supported by the wirelessdevice for the second technology. The transmit scenarios may correspondto various combinations of antennas (e.g., antennas 252 a through 252 rof FIG. 2 or antenna 303 of FIG. 3), frequency bands, channels, and/orbody positions.

The PD distribution (also referred to as a “PD map”) for each transmitscenario may be generated based on measurements (e.g., E-fieldmeasurements) performed in a test laboratory using a model of a humanbody. After the PD distributions are generated, the PD distributions maybe stored in the memory to enable the processor (e.g., processor 266 ofFIG. 2) to assess RF exposure in real time, as discussed further below.Each PD distribution includes a set of PD values, where each PD valuemay correspond to a different location (e.g., on the model of the humanbody).

The PD values in each PD distribution correspond to a particulartransmission power level (e.g., the transmission power level at whichthe PD values were measured in the test laboratory). Since PD scaleswith transmission power level, the processor may scale a PD distributionfor any transmission power level by multiplying each PD value in the PDdistribution by the following transmission power scaler:

$\begin{matrix}\frac{Tx_{c}}{Tx_{PD}} & (4)\end{matrix}$

where Tx_(c) is a current transmission power level for the respectivetransmit scenario, and TxPD is the transmission power levelcorresponding to the PD values in the PD distribution (e.g., thetransmission power level at which the PD values were measured in thetest laboratory).

As discussed above, the wireless device may support multiple transmitscenarios for the second technology. In certain aspects, the transmitscenarios may be specified by a set of parameters. The set of parametersmay include one or more of the following: (a) an antenna parameterindicating one or more antennas used for transmission (i.e., activeantennas), (b) a frequency band parameter indicating one or morefrequency bands used for transmission (i.e., active frequency bands),(c) a channel parameter indicating one or more channels used fortransmission (i.e., active channels), (d) a body position parameterindicating the location of the wireless device relative to the user'sbody location (head, trunk, away from the body, etc.), and/or (e) otherparameters. In cases where the wireless device supports a large numberof transmit scenarios, it may be very time-consuming and expensive toperform measurements for each transmit scenario in a test setting (e.g.,test laboratory). To reduce test time, measurements may be performed fora subset of the transmit scenarios to generate PD distributions for thesubset of transmit scenarios. In this example, the PD distribution foreach of the remaining transmit scenarios may be generated by combiningtwo or more of the PD distributions for the subset of transmitscenarios, as discussed further below.

For example, PD measurements may be performed for each one of theantennas to generate a PD distribution for each one of the antennas. Inthis example, a PD distribution for a transmit scenario in which two ormore of the antennas are active may be generated by combining the PDdistributions for the two or more active antennas.

In another example, PD measurements may be performed for each one ofmultiple frequency bands to generate a PD distribution for each one ofthe multiple frequency bands. In this example, a PD distribution for atransmit scenario in which two or more frequency bands are active may begenerated by combining the PD distributions for the two or more activefrequency bands.

In certain aspects, a PD distribution may be normalized with respect toa PD limit by dividing each PD value in the PD distribution by the PDlimit. In this case, a normalized PD value exceeds the PD limit when thenormalized PD value is greater than one, and is below the PD limit whenthe normalized PD value is less than one. In these aspects, each of thePD distributions stored in the memory may be normalized with respect toa PD limit.

In certain aspects, the normalized PD distribution for a transmitscenario may be generated by combining two or more normalized PDdistributions. For example, a normalized PD distribution for a transmitscenario in which two or more antennas are active may be generated bycombining the normalized PD distributions for the two or more activeantennas. For the case in which different transmission power levels areused for the active antennas, the normalized PD distribution for eachactive antenna may be scaled by the respective transmission power levelbefore combining the normalized PD distributions for the activeantennas. The normalized PD distribution for simultaneous transmissionfrom multiple active antennas may be given by the following:

$\begin{matrix}{{PD_{norm\_ combined}} = {\sum\limits_{i = 1}^{i = L}{\frac{Tx_{i}}{Tx_{PDi}} \cdot \frac{PD_{i}}{PD_{\lim}}}}} & (5)\end{matrix}$

where Palm is a PD limit, PD_(norm_combined) is the combined normalizedPD distribution for simultaneous transmission from the active antennas,i is an index for the active antennas, PD_(i) is the PD distribution forthe ith active antenna, Tx_(i) is the transmission power level for thei^(th) active antenna, TX_(PDi) is the transmission power level for thePD distribution for the i^(th) active antenna, and L is the number ofthe active antennas.

Equation (5) may be rewritten as follows:

$\begin{matrix}{{PD_{norm\_ combined}} = {\sum\limits_{i = 1}^{i = L}{\frac{Tx_{i}}{Tx_{PDi}} \cdot {PD}_{norm\_ i}}}} & \left( {6a} \right)\end{matrix}$

where PD_(norm) is the normalized PD distribution for the i^(th) activeantenna. In the case of simultaneous transmissions using multiple activeantennas at the same transmitting frequency (e.g., MIMO), the combinednormalized PD distribution is obtained by summing the square root of theindividual normalized PD distributions and computing the square of thesum, as given by the following:

$\begin{matrix}{{PD_{{norm\_ combined}{\_ MIMO}}} = {\left\lbrack {\sum\limits_{i = 1}^{i = L}\sqrt{\frac{Tx_{i}}{Tx_{PDi}} \cdot {PD}_{norm\_ i}}} \right\rbrack^{2}.}} & \left( {6b} \right)\end{matrix}$

In another example, normalized PD distributions for different frequencybands may be stored in the memory. In this example, a normalized PDdistribution for a transmit scenario in which two or more frequencybands are active may be generated by combining the normalized PDdistributions for the two or more active frequency bands. For the casewhere the transmission power levels are different for the activefrequency bands, the normalized PD distribution for each of the activefrequency bands may be scaled by the respective transmission power levelbefore combining the normalized PD distributions for the activefrequency bands. In this example, the combined PD distribution may alsobe computed using Equation (6a) in which i is an index for the activefrequency bands, PD_(norm_i) is the normalized PD distribution for thei^(th) active frequency band, Tx_(i) is the transmission power level forthe i^(th) active frequency band, and TX_(PDi) is the transmission powerlevel for the normalized PD distribution for the i^(th) active frequencyband.

Example Method to Distinguish between Cover and Human Grip

As noted above, in wireless communication, there is a maximumpermissible exposure (MPE) limit from international regulators,including the International Commission on Non-Ionizing RadiationProtection (ICNIRP) and the Federal Communications Commission (FCC) inthe United States, that specifies the highest power or energy density(in W/cm² or J/cm²) of an electromagnetic source that is consideredsafe. In some cases, the MPE limit(s) may be converted into a constraintrelated to the maximum transmission power by one or more devices (e.g.,depending on the implementation of each of the devices) and, thus, anuplink (UL) signal transmitted by a device may be limited due to MPEcompliance.

Some UEs may include sensors (e.g., millimeter wave (mmW) sensors) thatallow for higher UL transmission power levels if the sensor output showsno detection of an object blocking the UE antenna(s), potentiallyboosting UL throughput with transmission at such higher power levels.For example, FIG. 4A illustrates mmW sensing by a UE 120 using suchobject-detection sensors. In FIG. 4A, the UE 120 includes at least oneantenna array 400 with multiple antennas 402 a-d (collectively referredto herein as “antennas 402”). To detect an object 404 (shown in FIGS. 4Band 4C) or an open space (OS) condition, the UE 120 may output a signal(e.g., a continuous wave (CW), out-of-band signal) from one of theantennas 402 in the array 400 (e.g., from antenna 402 a) with aparticular detection angle 406, and another antenna (e.g., antenna 402d) in the array may receive signals reflected from the surface of anearby object 404, such as a protective cover or a human hand or finger.With the reflected signals, the UE 120 may utilize cross-polarization(Xpol) as illustrated in FIG. 4B with two polarized receive paths (onefor the horizontal polarization component (labeled “H-pol”) in thecircuit diagram 420 and another for the vertical polarization component(labeled “V-pol”) to determine a cross-polarization ratio(K=k_(V)/k_(H)) and detect whether an object 404 is present.Additionally or alternatively, the UE 120 may employ frequency-modulatedcontinuous-wave (FMCW) radar for object detection, as illustrated inFIG. 4C with the example frequency sweep and the circuit diagram 460. Asillustrated in FIG. 4A, Xpol may have an object detection radius 408ranging from 0 to about 4 cm from the UE 120, whereas FMCW radar mayhave an objection detection radius ranging from about 4 cm to about 60cm from the UE.

As explained above, FIG. 4B illustrates mmW sensing usingcross-polarization (Xpol) to detect an object 404 near a UE or to detectan OS condition, in accordance with certain aspects of the presentdisclosure. In FIG. 4B, the antenna array 400 comprises four antennas402, although any suitable number of antennas may be used. In thecircuit diagram 420, the transmit path (e.g., transmit path 302)includes a frequency synthesizer (e.g., the TX frequency synthesizer318) and an amplifier 421. The frequency synthesizer is used to generatea CW signal having a frequency (fcw) that is out of band, for example,between a first component carrier band (CC1) and a second componentcarrier band (CC2). In this example, fcw is 28 GHz. The amplifier 421may amplify the CW signal and drive the antenna 402 a to wirelesslytransmit the signal (e.g., with a particular detection angle 406).

If there is an object 404 near the UE, a surface of the object mayreflect the transmitted signal, and another antenna (e.g., antenna 402d) in the antenna array 400 may receive signals reflected from thesurface of the object. For Xpol detection, the receive path (e.g.,receive path 304) may include two polarized receive paths (one for thehorizontal polarization component (labeled “H-pol”) in the circuitdiagram 420 and another for the vertical polarization component (labeled“V-pol”). The H-pol receive path includes an amplifier (e.g., a lownoise amplifier 332 _(H)), a mixer 324 _(H), a filter (e.g., basebandfilter 326 _(H)), and an ADC 328 _(H). Similarly, the V-pol receive pathincludes an amplifier (e.g., a low noise amplifier 332 _(V)), a mixer324 _(V), a filter (e.g., baseband filter 326 _(V)), and an ADC 328_(V). A frequency synthesizer (e.g., an RX frequency synthesizer 330)may generate a local oscillator (LO) signal (e.g., having a frequency of28.001 GHz, offset 100 MHz from the transmitted signal) as an input toeach of the H-pol and V-pol mixers 324 _(H), 324 _(V). These receivechain components in FIG. 4B may function as described above with respectto FIG. 3, amplifying received RF signals, mixing the amplified RFsignals with the LO signal to downconvert the signals, filtering themixed signals to focus on the baseband signals, and digitizing thebaseband signals.

The H-pol and V-pol digitized signals from the ADCs may be sent to aprocessor 422, which may be implemented by a digital signal processor(DSP) or any other suitable processing system. The processor 422 mayinclude a fast Fourier transform (FFT) module 424 and a frequency-domainin-phase/quadrature (FD-IQ) module 426. The FFT module 424 may be usedto convert the time-domain digitized signals to frequency-domain data,which may yield a maximum H-pol FFT value (k_(H)) and a maximum V-polFFT value (k_(V)), as explained below with respect to FIG. 5. Using thefrequency-domain data, the FD-IQ module 426 may be used to plot thecross-polarization ratio (K=k_(V)/k_(H)) in the I/Q plane, asillustrated in the graph 430. Open space (i.e., no nearby object) mayhave a different location in the UQ plane than various objects, and inthis manner, Xpol may be used to determine whether an object is present.

As explained above, FIG. 4C illustrates mmW sensing using FMCW radar todetect an object 404 near a UE or to detect an OS condition, inaccordance with certain aspects of the present disclosure. In FIG. 4C,the antenna array 400 comprises four antennas 402, although any suitablenumber of antennas may be used. In the circuit diagram 460, the transmitpath (e.g., transmit path 302) includes a DAC 308, a baseband filter310, a mixer 312, and the amplifier 421, which may represent the DA 314and/or the PA 316. A frequency synthesizer 462 may be used to generatean LO signal for inputting to the mixer 312. The frequency synthesizer462, in conjunction with the other components of the transmit path, maybe used to generate a frequency sweep (e.g., from 25 to 29 GHz), whichmay include CC1 and CC2 bands as shown, in a wirelessly transmittedsignal output from the antenna 402 a, for example.

If there is an object 404 near the UE, a surface of the object mayreflect the transmitted signal, and another antenna (e.g., antenna 402d) in the antenna array 400 may receive signals reflected from thesurface of the object. For FMCW radar detection, the receive path (e.g.,receive path 304) may include a low noise amplifier 332, a mixer 324, abaseband filter 326), and an ADC 328. These receive path components inthe circuit diagram 460 of FIG. 4C may function as described above withrespect to FIG. 3, amplifying received RF signals, mixing the amplifiedRF signals with the LO signal from the frequency synthesizer 462 todownconvert the signals, filtering the mixed signals to focus on thebaseband signals, and digitizing the baseband signals. The FMCWdigitized signals from the ADC 328 may be sent to a processor 464, whichmay be implemented by a DSP or any other suitable processing system. Theprocessor 464 may process the FMCW digitized signals to detect an objector an open space condition.

FIG. 5 illustrates example FFT symbol values from Xpol detection, inaccordance with certain aspects of the present disclosure. The FFTsymbol values include horizontal polarization FFT values 510 based ondigitized signals from the H-pol receive path and vertical polarizationFFT values 520 based on digitized signals from the V-pol receive path.The maximum value of the horizontal polarization FFT values 610indicates k_(H), whereas the maximum value of the vertical polarizationFFT values 620 indicates k_(V). The cross-polarization ratio (K) isdetermined by K=k_(V)/k_(H).

The complex value of K (I+jQ) provides an indication of the presence ofan object in front of the antenna. k_(V)/k_(H) division (which may beimplemented as k_(V)/k_(H)*) may eliminate calibration of the transmitgain/phase randomness during each measurement. FIG. 6 is an example plot600 of multiple samples of K in the in-phase/quadrature (IQ) plane fortwo different scenarios: open space and a finger grip (or protectivecase).

The standard deviation of consecutive K measurements over time (σ_(K))provides a metric of stability of an object in front of the antenna. Inother words, a relatively larger σ_(K) means less object stability(i.e., more object movement), whereas a relatively smaller σ_(K)indicates greater stability (i.e., less object movement). Open space(i.e., no reflector) provides a relatively smaller σ_(K). A human fingeror hand not gripping the UE in front of an antenna provides a relativelylarger σ_(K), but a finger gripping the UE provides a relatively smallerσ_(K) because a finger does not move as much when part of a grip.Similar to a finger with grip, protective cases (e.g., made of plasticand/or glass) also provide smaller σ_(K), thereby making it difficult todifferentiate a protective cover from a human grip using only σ_(K). Forexample, as illustrated in the example plot 600 of FIG. 6, the σ_(K) foropen space may be similar to the σ_(K) for a protective case (or afinger grip).

A higher transmission power may be used by a UE when the antenna isblocked by a protective case, but a lower transmission power should beused when the antenna is blocked by a finger or other human tissue, dueto MPE limits, as described above. Therefore, what is needed aretechniques and apparatus for differentiating between a protective coverand human grip by object-detection sensors of a UE.

Furthermore, different protective cases may provide differentcross-polarization ratio centers {mean(K)} in the IQ plane. An algorithmfor determining transmission power may periodically adapt the open spaceparameters for a UE, which, when combined with the different K centersfor different protective cases, may also make it more difficult todifferentiate a protective case from finger grip.

Certain aspects of the present disclosure provide techniques andapparatus for distinguishing between an antenna of a UE being blocked bya cover (e.g., a protective rubber or plastic case) or by human tissue(e.g., a finger or palm) using at least two different types ofparameters, as described in greater detail below.

FIG. 7 is a flow diagram illustrating example operations 700 forwireless communications, in accordance with certain aspects of thepresent disclosure. The operations 700 may be performed, for example, bya wireless device (e.g., UE 120 of FIG. 1), and more particularly, by areceiver, processor, and transmitter of the wireless device.

The operations 700 may begin, at block 701, with the wireless devicetransmitting a first signal (e.g., with the TX front-end circuits254-254 r or the transmit path 302 of the UE 120) and, at block 702,receiving a plurality of signals (e.g., with the RX front-end circuits254-254 r or the receive path 304 of a UE 120) based on the transmittedfirst signal (e.g., reflections of the transmitted first signal). Atblock 704, the wireless device determines values for at least twodifferent types of parameters based on the received plurality of signals(e.g., with the receive processor 258, the control/processor 280, and/orthe transmit processor 264 or with the processor 422 of the UE 120). Atblock 706, the wireless device determines an environmental scenario forthe device based on the values for the at least two different types ofparameters (e.g., with the receive processor 258, the control/processor280, and/or the transmit processor 264 or with the processor 422 of theUE 120). At block 708, the wireless device transmits a second signalusing a transmission power based on the determined environmentalscenario (e.g., with the TX front-end circuits 254-254 r or the transmitpath 302 of the UE 120). The operations 700 are described in greaterdetail below and illustrated in the various drawings.

As presented above, σ_(K) may be insufficient to distinguish between aprotective cover and human grip. Therefore, certain aspects of thepresent disclosure provide another dimension of information in additionto σ_(K). For certain aspects, this additional information may bedetermined from the FFT data already provided by the two polarizedreceive paths.

For example, empirical studies show the signal-to-noise ratio (SNR) ofFFTs from H-pol and V-pol fluctuate with different types of objects. TheSNR of the vertical polarization component (SNR_(V)) may be expressed asSNR_(V)=10*log₁₀(k_(V)/σ² _(FFTV)), where σ² _(FFTV) is the variance ofthe vertical polarization FFT values (e.g., FFT values 520). The SNR ofthe horizontal polarization component (SNR_(H)) may be expressed asSNR_(H)=10*log₁₀(k_(H)/σ² _(FFTH)), where σ² _(FFTH) is the variance ofthe horizontal polarization FFT values (e.g., FFT values 510). The meanSNR (SNR_(m)) of these two SNRs may be expressed asSNR_(m)=SNR_(v)−(SNR_(H)-SNR_(V)). The processor (e.g., processor 422)calculating the FFT values may calculate the noise power of a number ofbins adjacent to the k_(H) or kv peak (e.g., 20 adjacent bins, 10 binson either side of the peak). For certain aspects, the processor mayremove or otherwise effectively ignore bins that have spurs.

Electromagnetic (EM) simulations show that the near-field coupledelectric field changes with the dielectric that mimics a human finger.The hypothesis for observed SNR fluctuations is that coupled signalpower fluctuates relative to a fixed receiver noise floor (e.g.,according to kTBFG, where k is Boltzmann's constant, T is absolutetemperature, F is the noise figure, B is the reception bandwidth, and Gis the gain) and has a correlation to the type of material due to thereflection coefficient of the material.

FIG. 8 is an example plot 800 of SNR in decibels (dB) of vertical andhorizontal polarization components for different scenarios, includingopen space (OS), grip, and protective case. Thus, with this additionalinformation, different environmental scenarios that produce the sameσ_(K) can be differentiated by also looking at SNR_(m).

FIG. 9 illustrates an example plot 900 of K for different scenarios inthe IQ plane. In the IQ plot 900, an orthogonal human finger pressedagainst the UE has a relatively very large σ_(K), as shown by the spreadof the K values. In contrast, open space and a human palm pressedagainst the UE have similar, relatively small σ_(K), and a rubberprotective case and a vertical human finger pressed on the UE have asimilar, albeit noticeably larger σ_(K). Therefore, considering onlyσ_(K) may make it difficult to distinguish between open space, aprotective case, or a human tissue condition.

FIG. 9 also illustrates a graph 950 showing an example correlationbetween σ_(K) and SNR_(m) for the same scenarios presented in the IQplot 900, in accordance with certain aspects of the present disclosure.Using regression or any of various other suitable techniques, a linearequation can be found to separate scenarios that may be categorized asOS (e.g., OS or protective cover) and scenarios that may be categorizedas object detection (e.g., presence of human tissue), for the purposesof determining transmission power. The line 952 represented by thislinear equation in the graph 950 may be considered as a boundaryseparating the two regions: an OS region versus an object detectionregion. The threshold standard deviation (σ_(TH)) of this OS/detectionboundary line 952 may be expressed as σ_(TH)=m*SNR_(m)+c, where m is theslope of the line and c is the σ_(K) offset.

FIG. 10 is a graph 1000 illustrating an example linear relationshipbetween σ_(K) and SNR_(m) for different scenarios (e.g., differentmaterials), where the line 1002 with equation σ_(TH)=m * SNR_(m)+crepresents a boundary between open space (OS) and object detectionregions, in accordance with certain aspects of the present disclosure.Note how air, the rubber protective case, and the plastic phone backhousing are in the OS region, whereas the pressed horizontal humanfinger, the pressed human palm, the pressed orthogonal human finger, andthe pressed vertical human finger are in the detection region. Thelinear equation may be frequency or band dependent. Additionally oralternatively, the linear equation may be dependent on the specific UE,varying between types, brands, and models.

FIG. 11 is a flow chart 1100 for determining parameters for OS based onσ_(K) and SNR_(m), in accordance with certain aspects of the presentdisclosure. The parameters for OS may include the radius (R_(OS)) andthe center (C_(OS)) of the OS. As shown in the flow chart 1100, ifσ_(K)<σ_(TH) (indicating the OS region), then the OS parameters may beupdated, where R_(OS)=3* σ_(K) and where C_(OS)=mean (K). Otherwise, theOS parameters are not updated, and more samples are captured. Morespecifically, samples (e.g., Xpol samples) are captured at block 1102,and an FFT is performed on the captured samples at block 1104 to convertthe sampled data from the time domain to the frequency domain. From theFFT, σ_(K) may be determined at block 1106, and the SNR_(m) may bedetermined at block 1108, as described above. At block 1110, thevariables (e.g., m and c) of the linear equation for the boundarybetween open space and object detection regions (e.g., line 952 or line1002) may be determined (e.g., read from memory, such as from memory282). At block 1112, σ_(TH) may be calculated using the variables forthe linear equation and SNR_(m). If σ_(K)<σ_(TH) (indicating the OSregion) as determined at block 1114, then the OS parameters are updatedat block 1116, where R_(OS)=3*σ_(K) and where C_(OS)=mean (K).Otherwise, if σ_(K)≥σ_(TH) as determined at block 1114, the OSparameters are not updated, and more samples are captured at block 1102.

As described above, certain aspects of the present disclosure aredirected to a method for wireless communications by a UE. The methodgenerally includes receiving a plurality of signals at the UE,determining values for at least two different types of parameters basedon the received plurality of signals, determining an environmentalscenario for the UE based on the values for the at least two differenttypes of parameters, and transmitting a signal using a transmissionpower based on the determined environmental scenario.

According to certain aspects, the received plurality of signals includesa vertical polarization component signal and a horizontal polarizationcomponent signal. For certain aspects, the at least two different typesof parameters comprise a statistic of a cross-polarization ratio betweenthe vertical polarization component signal and the horizontalpolarization component signal. For example, the statistic of thecross-polarization ratio may be a standard deviation of thecross-polarization ratio. For certain aspects, the at least twodifferent types of parameters further include a statistic of asignal-to-noise ratio based on the vertical polarization componentsignal and the horizontal polarization component signal. For example,the statistic of the signal-to-noise ratio may be a mean of thesignal-to-noise ratio calculated based on a variance of the verticalpolarization component signal and on a variance of the horizontalpolarization component signal.

According to certain aspects, the at least two different types ofparameters include a statistic of a signal-to-noise ratio based on thevertical polarization component signal and the horizontal polarizationcomponent signal.

According to certain aspects, receiving the plurality of signals entailsreceiving the vertical polarization component signal via a verticallypolarized receive path of the UE and receiving the horizontalpolarization component signal via a horizontally polarized receive pathof the UE.

According to certain aspects, the method further involves transmitting atest signal from the UE. In some cases, the test signal may be acontinuous wave (CW) signal or a frequency-modulated continuous-wave(FMCW) radar signal. For certain aspects, the test signal is transmittedfrom an antenna in an antenna array of the UE, and the plurality ofsignals is received by another antenna in the antenna array.

According to certain aspects, determining the environmental scenarioentails distinguishing between an antenna of the UE being blocked by acover or by human tissue. For example, the cover may include aprotective case for the UE.

According to certain aspects, determining the environmental scenarioinvolves determining a center and a radius of an open space from anantenna of the UE.

According to certain aspects, determining the environmental scenarioincludes determining a line (e.g., a line, such as line 952 or line1002) based on a linear relationship between the at least two types ofparameters and determining whether one of the at least two types ofparameters is above the line. In this case, the signal may betransmitted using a relatively lower transmission power if the one ofthe at least two types of parameters is above the line, whereas thesignal may be transmitted using a relatively higher transmission powerif the one of the at least two types of parameters is not above theline. For certain aspects, parameters of the line (e.g., the slope andthe offset) may be stored in memory.

According to certain aspects, determining the environmental scenarioinvolves determining a boundary based on a relationship between the atleast two types of parameters and determining whether one of the atleast two types of parameters is on a first side of the boundary or asecond side of the boundary. In this case, the signal may be transmittedusing a relatively lower transmission power if the one of the at leasttwo types of parameters is on the first side of the boundary, whereasthe signal may be transmitted using a relatively higher transmissionpower if the one of the at least two types of parameters is on thesecond side of the boundary.

According to certain aspects, determining the environmental scenarioinvolves determining a material of a protective case covering the UE.For certain aspects, the received plurality of signals includes avertical polarization component signal and a horizontal polarizationcomponent signal, and the at least two different types of parameterscomprise a statistic of a cross-polarization ratio between the verticalpolarization component signal and the horizontal polarization componentsignal. In this case, determining the material of the protective casecovering the UE may be based, at least in part, on the statistic of thecross-polarization ratio. For example, the statistic may be a standarddeviation of the cross-polarization ratio.

Example Cover Detection

As described above, demodulated signals in the complex IQ domain have aunique value for open space (with no object), a human object, or a cover(e.g., a protective case). Relative to a factory calibrated orcharacterized open space, both a human object and a cover may beinterpreted as objects triggering a detection. However, if the complexIQ domain value of the cover is known by the original equipmentmanufacturer (OEM), entry of this value to the UE detection algorithmmay be used to further differentiate the human object from the cover.

In cases were the unique value of the cover is not known, a detectiontechnique may be employed. For example, as described above, eachmaterial exhibits a relationship between the standard deviation (orvariance) of the complex IQ domain values (e.g., σ_(K)) and the SNRdifference between horizontal and vertical polarization components (asshown in FIGS. 6 and 9). For certain aspects, classification as openspace with covers and classification as detected objects with covers mayalso be differentiated by the detection algorithm querying a database ofcharacterized materials and scenarios (e.g., as depicted in FIGS. 9 and10).

The material of a protective cover covering the mmW antenna array (e.g.,array 400) can negatively impact the UE's performance. For certainaspects, a cover-material-specific antenna array codebook may beselected (instead of an array codebook intended for an uncovered UE)upon detecting the cover (or more specifically, the material composingthe cover) to improve performance. For example, the UE may bepreprogrammed with a codebook associated with specific complex IQ valuesof a known cover (e.g., a first-party cover). Upon detecting the cover'smaterial via the specific complex IQ values, the preprogrammed codebookmay be selected, which can improve mmW performance.

According to certain aspects, a cover-specific detection scheme (e.g.,based on a radio frequency identification (RFID) tag or the like) may beutilized in conjunction with the detection algorithm, as presentedabove. For example, covers with similar material detection properties(e.g., a first-party protective case and a third-party “knock-off” case,made of the same material(s) with similar dimensions) may be furtherverified if the cover includes some form of wireless ID included in atag. For certain aspects, the tag may also be preprogrammed to includematerial properties of the cover, which can be verified by the detectionalgorithm described herein to be used with selecting the appropriatearray codebook. The added layer of verification may, for example, assistwith safety compliance and/or allow for further tailored codebooks(e.g., cover-specific as compared to cover-material-specific).

FIG. 12 is a flow diagram of example operations 1200 for wirelesscommunications based on antenna array codebook selection, in accordancewith certain aspects of the present disclosure. The operations 1200 maybe performed, for example, by a wireless device (e.g., UE 120 of FIG.1), and more particularly, by a receiver, processor, and transmitter ofthe wireless device.

The operations 1200 may begin, at block 1201, with the wireless devicetransmitting a first signal (e.g., from the antenna array and with theTX front-end circuits 254-254 r or the transmit path 302 of the UE 120).At block 1202, the wireless device receives a plurality of signals(e.g., with the RX front-end circuits 254-254 r or the receive path 304of a UE 120) based on the transmitted first signal. At block 1204, thewireless device determines a value for each of one or more parametersbased on the received plurality of signals (e.g., with the processor422). At block 1206, the wireless device determines a type of a coveradjacent an antenna array of the device based on the value for each ofthe one or more parameters (e.g., with the processor 422). At block1208, the wireless device selects an antenna array codebook based on thedetermined type of the cover (e.g., with the processor 422). At block1210, the wireless device transmits a second signal (from the antennaarray) according to the selected antenna array codebook (e.g., with theTX front-end circuits 254-254 r or the transmit path 302 of the UE 120).

According to certain aspects, determining the type of the cover at block1206 entails determining a material of the cover. For example, thematerial of the cover may include at least one of plastic or rubber.

According to certain aspects, the cover includes a protective case forthe UE.

According to certain aspects, the received plurality of signals includesa vertical polarization component signal and a horizontal polarizationcomponent signal. For certain aspects, the one or more parametersinclude a statistic of a cross-polarization ratio between the verticalpolarization component signal and the horizontal polarization componentsignal. For example, the statistic of the cross-polarization ratio maybe a standard deviation of the cross-polarization ratio. For certainaspects, the value of the cross-polarization ratio is plotted in anin-phase/quadrature (IQ) plane over time. For certain aspects, the oneor more parameters further include a statistic of a signal-to-noiseratio based on the vertical polarization component signal and thehorizontal polarization component signal. In this case, the statistic ofthe signal-to-noise ratio may be a mean of the signal-to-noisecalculated based on a variance of the vertical polarization componentsignal and on a variance of the horizontal polarization componentsignal. For certain aspects, receiving the plurality of signals involvesreceiving the vertical polarization component signal via a verticallypolarized receive path of the UE and receiving the horizontalpolarization component signal via a horizontally polarized receive pathof the UE.

According to certain aspects, the first signal may be a test signaltransmitted from the wireless device. In this case, the transmitted testsignal may be reflected by the cover to generate the plurality ofsignals received at the device. The test signal may include, forexample, a continuous wave signal or a frequency-modulatedcontinuous-wave (FMCW) radar signal.

According to certain aspects, the operations 1200 further involvewirelessly reading an identification tag associated with the cover. Forexample, the identification tag may be a radio frequency identification(RFID) tag. For certain aspects, determining the type of the cover atblock 1206 entails comparing the type of the cover determined based onthe value for each of the one or more parameters with a type of thecover based on the read identification tag. For certain aspects, thecover is a protective case for the UE, and in this case, theidentification tag may indicate a particular model of the protectivecase.

Conclusion

Certain aspects of the present disclosure use a signal-processingalgorithm with statistics to differentiate between an antenna of a userequipment (UE) being blocked by a cover (e.g., a protective rubber orplastic case) or by human tissue (e.g., a finger or palm). This providesfor increased uplink (UL) throughput, while meeting regulatory RFexposure limits when the object is not present. As described above, anantenna array may transmit a weak CW signal from one of the antennastherein. One of the adjacent antennas in the array may receivenear-field mmW electromagnetic (EM) fields and monitor the perturbationof the EM fields by looking at complex FFT values of two polarizedreceivers (e.g., H-pol and V-pol receive paths). By analyzing thestandard deviation of the CW peak complex value and the SNR ratios ofthe two polarized receivers, aspects of the present disclosure maydetermine what type of material or hand grip is presented at or near thesurface of the antenna, or at least be able to distinguish between acover and human tissue.

The various operations of methods described above may be performed byany suitable means capable of performing the corresponding functions.The means may include various hardware and/or software component(s)and/or module(s), including, but not limited to a circuit, anapplication-specific integrated circuit (ASIC), or processor. Generally,where there are operations illustrated in figures, those operations mayhave corresponding counterpart means-plus-function. For example, meansfor receiving may include the RX front-end circuits 254-254 r of FIG. 2or the receive path 304 of FIG. 3. Means for transmitting may includethe TX front-end circuits 254-254 r of FIG. 2 or the transmit path 302of FIG. 3. Means for determining and/or means for selecting may includeat least one processor, such as the receive processor 258, thecontroller/processor 280, and/or the transmit processor 264 of FIG. 2 orthe processor 422 of FIG. 4B.

As used herein, the term “determining” encompasses a wide variety ofactions. For example, “determining” may include calculating, computing,processing, deriving, investigating, looking up (e.g., looking up in atable, a database, or another data structure), ascertaining, and thelike. Also, “determining” may include receiving (e.g., receivinginformation), accessing (e.g., accessing data in a memory), and thelike. Also, “determining” may include resolving, selecting, choosing,establishing, and the like.

As used herein, a phrase referring to “at least one of” a list of itemsrefers to any combination of those items, including single members. Asan example, “at least one of: a, b, or c” is intended to cover: a, b, c,a-b, a-c, b-c, and a-b-c, as well as any combination with multiples ofthe same element (e.g., a-a, a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b,b-b-b, b-b-c, c-c, and c-c-c or any other ordering of a, b, and c).

The various illustrative logical blocks, modules, and circuits describedin connection with the present disclosure may be implemented orperformed with a general purpose processor, a digital signal processor(DSP), an ASIC, a field programmable gate array (FPGA) or otherprogrammable logic device (PLD), discrete gate or transistor logic,discrete hardware components, or any combination thereof designed toperform the functions described herein. A general-purpose processor maybe a microprocessor, but in the alternative, the processor may be anycommercially available processor, controller, microcontroller, or statemachine. A processor may also be implemented as a combination ofcomputing devices, e.g., a combination of a DSP and a microprocessor, aplurality of microprocessors, one or more microprocessors in conjunctionwith a DSP core, or any other such configuration.

The methods disclosed herein comprise one or more steps or actions forachieving the described method. The method steps and/or actions may beinterchanged with one another without departing from the scope of theclaims. In other words, unless a specific order of steps or actions isspecified, the order and/or use of specific steps and/or actions may bemodified without departing from the scope of the claims.

The functions described may be implemented in hardware, software,firmware, or any combination thereof If implemented in hardware, anexample hardware configuration may comprise a processing system in awireless node. The processing system may be implemented with a busarchitecture. The bus may include any number of interconnecting busesand bridges depending on the specific application of the processingsystem and the overall design constraints. The bus may link togethervarious circuits including a processor, machine-readable media, and abus interface. The bus interface may be used to connect a networkadapter, among other things, to the processing system via the bus. Thenetwork adapter may be used to implement the signal processing functionsof the physical (PHY) layer. In the case of a user terminal, a userinterface (e.g., keypad, display, mouse, joystick, etc.) may also beconnected to the bus. The bus may also link various other circuits suchas timing sources, peripherals, voltage regulators, power managementcircuits, and the like, which are well known in the art, and therefore,will not be described any further.

The processing system may be configured as a general-purpose processingsystem with one or more microprocessors providing the processorfunctionality and external memory providing at least a portion of themachine-readable media, all linked together with other supportingcircuitry through an external bus architecture. Alternatively, theprocessing system may be implemented with an ASIC with the processor,the bus interface, the user interface in the case of an accessterminal), supporting circuitry, and at least a portion of themachine-readable media integrated into a single chip, or with one ormore FPGAs, PLDs, controllers, state machines, gated logic, discretehardware components, or any other suitable circuitry, or any combinationof circuits that can perform the various functionality describedthroughout this disclosure. Those skilled in the art will recognize howbest to implement the described functionality for the processing systemdepending on the particular application and the overall designconstraints imposed on the overall system.

It is to be understood that the claims are not limited to the preciseconfiguration and components illustrated above. Various modifications,changes, and variations may be made in the arrangement, operation, anddetails of the methods and apparatus described above without departingfrom the scope of the claims.

What is claimed is:
 1. A method for wireless communications by awireless device, comprising: wirelessly reading an identification tagassociated with a cover covering at least a portion of the wirelessdevice; determining a type of the cover based on the identification tagassociated with the cover; and transmitting a signal using atransmission power based on the determined type of the cover.
 2. Themethod of claim 1, wherein the cover is a protective case for thewireless device and wherein the identification tag indicates aparticular model of the protective case.
 3. The method of claim 1,further comprising selecting an antenna array codebook, from a pluralityof predefined antenna array codebooks, based on the determined type ofthe cover, wherein the transmitting comprises transmitting the signalaccording to the selected antenna array codebook.
 4. The method of claim1, wherein determining the type of the cover comprises comparing thetype of the cover determined based on the identification tag with a typeof the cover determined using a detection technique.
 5. The method ofclaim 4, wherein the detection technique comprises: transmitting anothersignal from the wireless device; receiving a plurality of signals at thewireless device based on the transmitted other signal, wherein thereceived plurality of signals comprises a vertical polarizationcomponent signal and a horizontal polarization component signal; anddetermining the type of the cover based on the vertical polarizationcomponent signal and the horizontal polarization component signal. 6.The method of claim 5, wherein the type of the cover is determined inthe detection technique based on at least one of: a statistic of across-polarization ratio between the vertical polarization componentsignal and the horizontal polarization component signal; or a statisticof a signal-to-noise ratio based on the vertical polarization componentsignal and the horizontal polarization component signal.
 7. The methodof claim 1, wherein the identification tag indicates one or moreproperties of the cover.
 8. The method of claim 1, wherein theidentification tag indicates a material of the cover.
 9. The method ofclaim 1, wherein the transmission power is based on the determined typeof the cover and on radio frequency (RF) exposure limits.
 10. Anapparatus for wireless communications, comprising: a receiver configuredto wirelessly read an identification tag associated with a covercovering at least a portion of the apparatus; a processing systemconfigured to: determine a type of the cover based on the identificationtag associated with the cover; and determine a transmission power basedon the determined type of the cover; and a transmitter configured totransmit a signal from the apparatus using the determined transmissionpower.
 11. The apparatus of claim 10, wherein the cover is a protectivecase for the apparatus and wherein the identification tag indicates aparticular model of the protective case.
 12. The apparatus of claim 10,further comprising an antenna array coupled to the transmitter, wherein:the processing system is further configured to select an antenna arraycodebook, from a plurality of predefined antenna array codebooks, basedon the determined type of the cover; and the transmitter is configuredto transmit the signal via the antenna array according to the selectedantenna array codebook.
 13. The apparatus of claim 10, wherein todetermine the type of the cover, the processing system is configured tocompare the type of the cover determined based on the identification tagwith a type of the cover determined using a detection technique.
 14. Theapparatus of claim 13, wherein to perform the detection technique: thetransmitter is further configured to transmit another signal from theapparatus; the receiver is further configured to receive a plurality ofsignals based on the transmitted other signal, wherein the receivedplurality of signals comprises a vertical polarization component signaland a horizontal polarization component signal; and the processingsystem is further configured to determine the type of the cover in thedetection technique based on the vertical polarization component signaland the horizontal polarization component signal.
 15. The apparatus ofclaim 14, wherein the processing system is configured to determine thetype of the cover in the detection technique based on at least one of: astatistic of a cross-polarization ratio between the verticalpolarization component signal and the horizontal polarization componentsignal; or a statistic of a signal-to-noise ratio based on the verticalpolarization component signal and the horizontal polarization componentsignal.
 16. The apparatus of claim 10, wherein the identification tagindicates one or more properties of the cover.
 17. The apparatus ofclaim 10, wherein the identification tag indicates a material of thecover.
 18. The apparatus of claim 10, further comprising an antennaarray coupled to the transmitter, wherein the transmitter is configuredto transmit the signal from the apparatus via the antenna array usingthe determined transmission power and wherein the signal comprises abeamformed signal or a millimeter wave signal.
 19. The apparatus ofclaim 10, wherein the processing system is configured to determine thetransmission power based on the determined type of the cover and onradio frequency (RF) exposure limits.
 20. A non-transitorycomputer-readable medium storing code for wireless communications by awireless device, the code comprising instructions executable by at leastone processor to cause the wireless device to: wirelessly read anidentification tag associated with a cover covering at least a portionof the wireless device; determine a type of the cover based on theidentification tag associated with the cover; and transmit a signalusing a transmission power based on the determined type of the cover.